1. Field of the Invention
The present invention relates to a semiconductor photoelectric conversion device which has at least one PIN structure in which a p-type, I-type and N-type non-single-crystal semiconductor layers are laminated in that order or in the reverse order. Further, the invention pertains to manufacturing method of such a semiconductor photoelectric conversion device.
2. Description of the prior Art
Heretofore, a wide variety of semiconductor photoelectric conversion devices have been proposed which are of the type having at least one PIN structure such as mentioned above.
The semiconductor photoelectric conversion device has a mechanism that creates, by an incidence of light, carriers, i.e. electron-hole pairs in the I-type non-single-crystal semiconductor layer of the PIN structures and directs electrons and holes of the electron-hole pairs to the N-type and P-type non-single-crystal semiconductor layers, respectively, generating photovoltaic power. Accordingly, in order for the device to obtain a high photoelectric conversion efficiency, it is desirable that the I-type non-single-crystal semiconductor layer has no recombination centers with which the carriers are recombined.
One solution that has been proposed to meet such a requirement is a semiconductor photoelectric conversion device which has the I-type non-single-crystal semiconductor layer of its PIN structure doped with hydrogen serving as a recombination center neutralizer which combines with the recombination centers to neutralize them.
Further, it is desirable for achieving a high photoelectric conversion efficiency that the I-type non-single-crystal semiconductor layer does not contain an impurity which reduces carrier mobility.
The P-type, I-type and N-type non-single-crystal semiconductor layers of the PIN structure are each formed in a reaction chamber by means of a CVD, photo CVD, Plasma CVD or like method. In this case, since air and oil components are likely to remain in the reaction chamber, the I-type non-single-crystal semiconductor layer contains, as an impurity, oxygen and/or nitrogen, which decreases the carrier mobility. In the prior art photoelectric conversion devices, the concentration of such an impurity is as high as 5.times.10.sup.18 or more through out the I-type layer in its thickwise direction.
Accordingly, the conventional devices have the defect of low photoelectric conversion efficiency for the reason that the I-type layer of the PIN structure contains the impurity in such a high concentration as mentioned above.
Moreover, in the conventional devices, the I-type layer of the PIN structure contains the recombination center neutralizer, as referred to above. However, when the devices are exposed to radiant rays such as protons and .gamma. rays, neutron rays or electron rays, the combination of the recombination center and the recombination center neutralizer and the combination of semiconductor elements are destroyed by the rays, newly creating a large number of recombination centers.
Accordingly, the prior art devices possess the shortcoming that the photoelectric conversion efficiency is lowered by the incidence of radiant, neutron or electron rays though the I-type layer of the PIN structure contains the recombination center neutralizer.